1. Field of the Invention
This invention relates to a removal preventing mechanism for a bicycle hub assembly More specifically, the invention relates to a removal preventing mechanism for preventing unexpected removal of a hub assembly, particularly a quick-release type hub assembly, from the bicycle fork ends during running.
2. Description of the Prior Art
In bicycles, generally, it is often required to remove a hub assembly from a pair of fork ends of a bicycle frame for repair or replacement for example. For this purpose, Japanese Utility Model Application Laid-open No. 57-12301 (Laid-open: Jan. 22, 1982; Inventor: Keizo SHIMANO) discloses a quick-release type clamping assembly for a bicycle hub assembly which enables quick removal of the hub assembly when required.
More particularly, the clamping assembly of the above laid-open utility model application comprises a tie rod extending through a hollow hub shaft on which is rotatably supported a hub shell between a pair of fork ends. The tie rod has one end screwed to an adjusting end nut positioned axially outwardly from one fork end. The other end of the tie rod is provided with an enlarged head positioned axially outwardly from the other fork end and having a cam hole extending transversely of the rod. A hollow presser member is fitted around the enlarged head and axially movable relative thereto toward and away from the end nut. A lever, which is pivotable about a pivotal axis between a clamping position and a releasing position, is mounted to the presser member and has a cam portion received within the cam hole and eccentric relative to the pivotal axis.
When the lever is pivoted to the clamping position, the presser member is moved axially inwardly toward the end nut due to the eccentricity of the cam portion. As a result, the distance between the end nut and the presser member is reduced to clam the hub assembly to the fork ends.
Conversely, when the lever is pivoted to the releasing position, the presser member is moved axially outwardly away from the end nut, so that the hub assembly and the fork ends are relieved from the previous clamping force to enable removal of the hub assembly from the fork ends.
As described above, the quick-release type clamping assembly has an advantage of enabling quick mounting and removal of the hub. However, in such a clamping assembly, it is necessary to properly adjust the clamping force by previously selecting the initial axial position of the adjusting end nut on the tie rod. If this initial adjustment is improper, the clamping force may be insufficient for firmly clamping the hub assembly to the fork ends. Therefore, the hub assembly together with the wheel thereon may unexpectedly come off the fork ends during riding.
The problem of unexpected removal of the hub assembly is particularly serious with respect to off-road bicycles (often referred to as "mountain bicycles") which are designed to run on severely rough grounds. In such a bicycle, great shocks and vibrations frequently applied to the hub assembly causes loosening of the clamping assembly, thereby leading to unexpected removal of the hub assembly. Further, it is highly likely in the mountain bicycle that the lever of the quick-release type clamping assembly may come into accidental contact with an external object, so that the lever may be pivoted in the releasing direction to allow removal of the hub assembly.
In view of the above problem, the applicant has previously proposed two different solutions for preventing unexpected removal of the hub assembly from the bicycle fork ends. A first solution is disclosed in Japanese Utility Model Application Laid-open No. 62-127004 (Laid-open: Aug. 12, 1987), whereas a second solution is disclosed in disclosed in U.S. Pat. No. 4,906,053 issued on Mar. 6, 1990.
According to the first solution, use is made of a stopper washer which is fitted on the tie rod of the quick-release type clamping assembly (having the same structure as already described). The stopper washer has an engaging pawl which is made to engage a suitable portion of a fork end, so that the hub assembly associated with the clamping assembly is prevented from unexpected removal by the stopper washer engaging the fork end.
However, the first solution, while effective for preventing unexpected removal of the hub assembly, is defective in that the stopper washer must be angularly adjusted to engage a suitable portion of the fork end at the time of mounting and re-mounting the hub assembly relative to the fork end. Obviously, the necessity for angular adjustment detracts much from the quick operability of the quick-release type clamping assembly.
The second solution utilizes a cap-shaped hub stopper which is fitted around the adjusting end nut of the quick-release type clamping assembly. The hub stopper is slidably movable on the end nut axially of the hub assembly between a first position for surrounding engagement with a fork end and a second position for disengaging from the fork end. The hub stopper is held in a selected one of the first and second positions by locking means.
The second solution, while also effective for preventing unexpected removal of the hub assembly, is defective in that the adjusting nut must be re-designed in configuration to enable slidable fitting of the hub stopper and mounting of the locking means for the hub stopper. Further, the second solution is also disadvantageous in that a similar hub stopper cannot be arranged on the presser member of the quick-release type clamping assembly because the presence of the lever prohibits or restricts slidable fitting of the hub stopper onto the presser member.